Power transmitting apparatuses

ABSTRACT

A power transmitting apparatus for a vehicle mounted with a torque converter and an idle-stop mechanism can be configured to improve fuel economy without cancelling a fuel-cut-ff during vehicle speed reduction and to reduce the manufacturing cost by eliminating an electrically-driven oil pump. A power transmitting apparatus can comprise a torque converter, a clutch mechanism, an oil pump, a continuously variable transmission, a clutch control device, an engine control device, and a flow control device. The flow control device can be configured to limit or prevent the supply of oil to the torque converter by the oil pump and to prioritize the supply of oil to the clutch mechanism and the continuously variable transmission when the vehicle speed is reduced below a predetermined value with fuel being cut off by the engine control device during vehicle speed reduction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/235,157, filed Sep. 16, 2011, which is a continuation of PCTApplication No. PCT/JP2010/054513, filed on Mar. 17, 2010, which claimspriority to Japanese Application No. 2009-066747, filed on Mar. 18,2009, the entire contents of each of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTIONS

1. Field of the Inventions

The present inventions relate to power transmitting apparatuses, such asvehicle transmissions, which transmit power from an engine of a vehicleto the wheels of the vehicle and which are configured to properly selecttransmission of power and cutting-off of power to or from the wheels.

2. Description of the Related Art

Two types of known power transmitting apparatuses for vehicles (e.g.,“automatic transmissions”) provide starting power (power for initiatingmovement of the vehicle from a stop) in different ways. One type uses atorque converter (“torque converter type”) and another type uses astarting clutch (“starting clutch type”) to provide starting power usedto start the movement of the vehicle from a stop. In the torqueconverter type devices, the starting performance benefits from thetorque amplifying function of the torque converter. On the other hand,the starting clutch type benefits from increased efficiency because thistype of system does not continuously lose power through slippage whichoccurs in the torque converter types e.g. during a steady running ofvehicle.

Japanese Laid-open Patent Publication No. 3193/2005 discloses a powertransmitting apparatus which is a torque converter type automatictransmission combined with a lock-up clutch. In this transmission, thelock-up clutch has a clutch piston connected to a turbine of a torqueconverter and is movable between a connected position in which it abutsagainst the inner circumferential surface of a torque converter coverand a non-connected separated position. Thus, the torque converter coverand the turbine can be directly connected and disconnected via theclutch piston.

Japanese Laid-open Patent Publication No. 328980/2000 discloses a powertransmitting apparatus of the torque converter type having an idle-stopfunction for automatically stopping an engine when a vehicle is stopped.This power transmitting apparatus comprises a continuously variabletransmission (sometimes called a “CVT”) and an oil pump driven by powerfrom the engine to supply the CVT and a clutch mechanism with oil andconfigured to operate the CVT, the clutch mechanism, and the torqueconverter.

SUMMARY OF THE INVENTIONS

An aspect of at least one of the inventions disclosed herein includesthe realization that a power transmitting apparatus for a vehicle with atorque converter and an idle-stop mechanism can be configured to improvefuel consumption by avoiding cancellation of fuel-cut-off during vehiclespeed reduction without adding an electrically-driven oil pump.

In the power transmitting apparatus of the prior art, when thetransmission ratio (effective gear ratio) of a CVT must be changed(e.g., to a lower transmission ratio (larger number ratio) inpreparation for the next initiation of movement) and vehicle speed hasbeen reduced below a predetermined value because fuel has been cut offfrom an engine during vehicle speed reduction, then engine speed (RPM)must be temporally increased by cancelling the fuel-cut-off (i.e.resuming of fuel injection), which disadvantageously deteriorates fueleconomy.

More specifically, since the rotation, and thus the operation, of an oilpump would be substantially reduced when vehicle speed is reduced belowa predetermined value and, accordingly, changing the CVT transmissionratio would become impossible, it is necessary to cancel thefuel-cut-off to temporally increase the engine speed so that the oilpump would be able to operate sufficiently. For a vehicle performing anidle-stop in particular, it is necessary to change to a lowertransmission ratio during vehicle speed reduction to prepare for thenext initiation of vehicle movement since operation of the CVT would beimpossible because the engine would be stopped while the vehicle isstopped.

Although it is possible to change the transmission ratio of the CVTduring vehicle operation regardless of the engine speed (or speed ofvehicle) without canceling fuel-cut-off by providing with anelectrically-driven oil pump separate from the engine-driven oil pump,this would disadvantageously increase of the manufacturing cost of thepower transmitting apparatus due to the addition of theelectrically-driven oil pump.

Thus, in accordance with an embodiment, a power transmitting apparatuscan comprise a torque converter having a torque amplifying function, aclutch mechanism, an oil pump, a continuously variable transmission, aclutch control device, an engine control device, and a flow controldevice. The clutch mechanism can be configured to be positioned in afirst power transmitting condition in which driving power of an engineis transmitted to driving wheels via a power transmitting system of thetorque converter and a second power transmitting condition in which thedriving power of the engine is transmitted to the wheels without thepower transmitting system of the torque converter. The oil pump can bedriven by the driving power of the engine to supply oil to the clutchmechanism and the torque converter to operate them. The continuouslyvariable transmission can be supplied with oil by the oil pump toactuate pulleys by hydraulic pressure of the oil to continuously varythe transmission ratio. The clutch control device can be configured toselectively operate the clutch mechanism in accordance with a vehiclecondition to position the clutch mechanism either in the first powertransmitting condition or the second power transmitting condition. Theengine control device can be configured to idle-stop the engine byautomatically stopping the engine when vehicle speed is reduced below apredetermined value and to restart the engine when the accelerator pedalis depressed or the brakes are released during an idle-stoppedcondition. The flow control device can be configured to limit or preventthe supply of oil to the torque converter by the oil pump and toprioritize the supply of oil to the clutch mechanism and thecontinuously variable transmission when the vehicle speed is reducedbelow a predetermined value with fuel being cut off by the enginecontrol device during vehicle speed reduction.

In some embodiments, the flow control device can comprise a hydraulicvalve mechanism having a first supply path configured to normally supplyoil to the torque converter, a second supply path configured to limit orprevent the supply of oil, and a valve configured to open and close thefirst supply path by hydraulic pressure.

In some embodiments, the valve can be normally urged in a direction forclosing the first supply path.

In some embodiments, the power transmitting apparatus can furthercomprise an accumulator configured to accumulate the oil and can beconfigured so that the oil accumulated in the accumulator is dischargedtherefrom to the clutch mechanism and the continuously variabletransmission when the vehicle speed is reduced below a predeterminedvalue with fuel to the engine being cut off during a process of vehiclespeed reduction.

In some embodiments, the clutch mechanism can comprise a first clutchdevice operated during forward vehicle operation and configured totransmit the driving power of the engine to the driving wheels via thepower transmitting system of the torque converter and a second clutchdevice operated during forward vehicle operation and configured totransmit the driving power of the engine to the driving wheels withoutthe power transmitting system of the torque converter, the clutchcontrol device can be configured to selectively operate the first clutchdevice and the second clutch device in accordance with the vehiclecondition to position them in either the first power transmittingcondition or the second power transmitting condition, and the clutchcontrol device can be configured to operate only the second clutchdevice when the vehicle speed is reduced below a predetermined valuewith fuel to the engine being cut off during a process of vehicle speedreduction.

In some embodiments, the power transmitting apparatus can furthercomprise a first driving shaft connected to the first clutch device anda second driving shaft connected to the second clutch device. The firstdriving shaft can be configured to be rotated by the driving power ofthe engine via the power transmitting system of the torque converter.The second driving shaft can be configured to be rotated by the drivingpower of the engine without the power transmitting system of the torqueconverter. The first and second driving shafts can be arranged coaxiallywith each other.

In some embodiments, the clutch mechanism can comprise aforward-operation clutch device operated during forward vehicleoperation and a lock-up clutch device. The forward-operation clutchdevice can be configured to transmit the driving power of the engine tothe driving wheels via the power transmitting system of the torqueconverter. The lock-up clutch device can be configured to transmit thedriving power of the engine to the driving wheels without the powertransmitting system of the torque converter. The clutch control devicecan be configured to selectively operate the forward-operation clutchdevice and the lock-up clutch device in accordance with the vehiclecondition to position them in either the first power transmittingcondition or the second power transmitting condition.

In some embodiments, the engine control device can prompt an idle-stopwhen the transmission ratio of the continuously variable transmission isa predetermined value or more.

In some embodiments wherein the power transmitting apparatus furthercomprises a flow control device configured to limit or prevent thesupply of oil to the torque converter by the oil pump and to prioritizethe supply of oil to the clutch mechanism and the continuously variabletransmission when the vehicle speed is reduced below a predeterminedvalue with fuel being cut off by the engine control device duringvehicle speed reduction, it is possible in a power transmittingapparatus for a vehicle mounted with a torque converter and an idle-stopmechanism to improve fuel economy without cancelling the fuel-cut-offduring vehicle speed reduction and to reduce the manufacturing cost byeliminating an electrically driven oil pump.

In some embodiments where the flow control device comprises a hydraulicvalve mechanism having a first supply path configured to normally supplyoil to the torque converter, a second supply path configured to limit orprevent the supply of oil, and a valve configured to open and close thefirst supply path by hydraulic pressure, it is possible instantly andsmoothly switch between the condition in which the supply of oil to thetorque converter is limited or prevented and the condition in which thesupply of oil to the torque converter is not limited or prevented.

In some embodiments where the valve is normally urged in a direction forclosing the first supply path, the supply of oil to the torque convertercan be reliably limited or prevented regardless of the response of thevalve when the vehicle speed is reduced below a predetermined value withfuel to the engine being cut off during the vehicle speed reduction.

In some embodiments wherein the power transmitting apparatus comprisesan accumulator configured to accumulate the oil and is configured sothat the oil accumulated in the accumulator is discharged therefrom tothe clutch mechanism. and the continuously variable transmission whenthe vehicle speed is reduced below a predetermined value with fuel tothe engine being cut off during vehicle speed reduction, oil can besupplied instantly and smoothly to the clutch mechanism and the CVT.

In some embodiments wherein the clutch mechanism comprises a firstclutch device operated during forward vehicle operation and configuredto transmit the driving power of the engine to the driving wheels viathe power transmitting system of the torque converter and a secondclutch device operated during forward vehicle operation and configuredto transmit the driving power of the engine to the driving wheelswithout the power transmitting system of the torque converter, and theclutch control device is configured to selectively operate the firstclutch device and the second clutch device in accordance with thevehicle condition to position them in either the first powertransmitting condition or the second power transmitting condition, it ispossible to avoid complication and increases in size of the powertransmitting apparatus, to improve the starting performance due to thetorque amplifying function of the torque converter, and to improve thepower transmitting efficiency during the steady running of a vehicle. Inembodiments where the clutch control device is also configured tooperate only the second clutch device when the vehicle speed is reducedbelow a predetermined value with fuel to the engine being cut off duringvehicle speed reduction, oil can be more reliably and smoothly supplied.

In some embodiments wherein the power transmitting apparatus furthercomprises a first driving shaft connected to the first clutch device andconfigured to be rotated by the driving power of the engine via thepower transmitting system of the torque converter, and a second drivingshaft connected to the second clutch device and configured to be rotatedby the driving power of the engine without the power transmitting systemof the torque converter, and the first and second driving shafts arearranged coaxially with each other, it is possible to reduce the wholesize of the power transmitting apparatus as compared with the size of apower transmitting apparatus in which the first and second drivingshafts extend linearly from each other.

In some embodiments wherein the clutch mechanism comprises aforward-operation clutch device operated during forward vehicleoperation and configured to transmit the driving power of the engine tothe driving wheels via the power transmitting system of the torqueconverter and a lock-up clutch device configured to transmit the drivingpower of the engine to the driving wheels without the power transmittingsystem of the torque converter, and the clutch control device isconfigured to selectively operate the forward-operation clutch deviceand the lock-up clutch device in accordance with the vehicle conditionto position them in either the first power transmitting condition or thesecond power transmitting condition, it is possible to easily apply sucha power transmitting apparatus to a vehicle mounted with a lock-upclutch device being comparatively in wide use.

In some embodiments where the engine control device prompts an idle-stopwhen the transmission ratio of the continuously variable transmission isa predetermined value or more, the appropriate driving power can beproduced when restarting an engine after an idle-stop.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view showing a power transmittingapparatus according to a first embodiment.

FIG. 2 is a schematic diagram of the power transmitting apparatus ofFIG. 1.

FIG. 3 is an enlarged cross-sectional view showing a clutch mechanism ofthe power transmitting apparatus of FIG. 1.

FIG. 4 is a cross-sectional view taken along a line IV-IV of FIG. 1.

FIG. 5 is an enlarged view of the clutch mechanism of the powertransmitting apparatus of FIG. 1 showing a condition in which only thefirst clutch device is activated.

FIG. 6 is an enlarged view of the clutch mechanism of the powertransmitting apparatus of FIG. 1 showing a condition in which only thesecond clutch device is activated.

FIG. 7 is an enlarged view of the clutch mechanism of the powertransmitting apparatus of FIG. 1 showing a condition in which both thefirst and second clutch devices are activated.

FIG. 8 is a schematic diagram of a power transmitting apparatusincluding a variable speed unit A.

FIG. 9 is a block diagram showing a hydraulic pressure control circuitof the power transmitting apparatus of FIG. 1.

FIG. 10 is a control mode table of a clutch control device of the powertransmitting apparatus of FIG. 1.

FIG. 11 is a time chart of the power transmitting apparatus of FIG. 1.

FIG. 12 is another time chart of the power transmitting apparatus ofFIG. 1.

FIG. 13 is a flowchart illustrating a control routine of an enginecontrol device of the power transmitting apparatus of FIG. 1.

FIG. 14 is a flowchart illustrating a control routine of a clutchcontrol device of the power transmitting apparatus of FIG. 1.

FIG. 15 is a block diagram showing a hydraulic pressure control circuitof a power transmitting apparatus of a second embodiment.

FIG. 16 is a time chart of the power transmitting apparatus of FIG. 15.

FIG. 17 is a schematic diagram of a power transmitting apparatus of athird embodiment.

DETAILED DESCRIPTION OF EXEMPLIFYING EMBODIMENTS

A first embodiment of a power transmitting apparatus can be configuredto transmit or cut-off the driving force from an engine (driving source)of an automobile (vehicle) to or from the wheels (driving wheels). Suchan apparatus can include, with reference to FIGS. 1 and 2, a torqueconverter 1, a clutch mechanism 3, an oil pump 31, a clutch controldevice 4, an engine control device 22, a flow control device 23, a firstdriving shaft 5, a second driving shaft 6, a damper mechanism 7, and athird clutch device 8, 8, and a variable speed unit A (continuouslyvariable transmission (CVT) 25). FIG. 1 is a longitudinal-section viewshowing a main part of the power transmitting apparatus of the firstembodiment, and FIG. 2 is a schematic diagram of the power transmittingapparatus of FIG. 1.

As shown in FIG. 2, the torque converter 1 and a transmission 2 areconfigured to perform as a power transmitting system that transmitspower from the engine E as the driving source of a vehicle to wheels(driving wheels D). The transmission 2 can include the clutch mechanism3, the third clutch device 8, and the variable speed unit A. In FIG. 1 areference numeral 11 denotes an input shaft extending from the engine Eand a reference numeral 9 denotes an output shaft extending to thevariable speed unit A.

The torque converter 1 can provide a torque amplifying function foramplifying the torque from the engine E and transmitting it to thetransmission 2. The torque converter 1 is rotated around its shaft bythe driving power transmitted from the engine E. The torque converter 1can comprise torque converter covers 1 a and 13 for containing oil(operating oil) in a fluid-tight manner. A pump P can be formed on thetorque converter cover 1 a and rotated together with the torqueconverter cover 1 a. A turbine T can be arranged oppositely to the pumpP and rotatable at a side of the torque converter cover 13.

The input shaft 11 can be connected to the torque converter cover 13through a cover member 12. When the input shaft 11 is rotated by thedriving power of the engine E, the cover member 12, the torque convertercovers 13 and 1 a, and the pump P are rotated. The rotational torque isthus transmitted to the turbine T through the oil (operating oil) withthe torque being amplified. The turbine T is then rotated by theamplified torque and thus the amplified torque is transmitted to thetransmission 2 through a first driving shaft 5 spline-fitted with theturbine T (first power transmitting condition). The term “powertransmitting system of the torque converter” used herein means a powertransmitting system formed by the torque converter cover 1 a, the pumpP, and turbine T. A reference numeral 10 in FIG. 1 denotes atransmission case.

On the other hand, the torque converter cover 13 can be connected to aconnecting member 14 through the damper mechanism 7 comprising coilsprings and the connecting member can be further spline-fitted with theouter circumferential surface of a second driving shaft 6. Accordingly,when the input shaft 11 is rotated by the driving power of the engine E,the cover member 12, the torque converter cover 13, the connectingmember 14 and the second driving shaft 6 are rotated and thus thedriving torque of the engine E is transmitted to the transmission 2.That is, the second driving shaft 6 can transmit the driving power tothe transmission 2 without through the power transmitting system of thetorque converter 1 (second power transmitting condition).

As described above, the first driving shaft 5 can be rotated by thedriving power of the engine E through the power transmitting system ofthe torque converter 1 and can be connected to a first clutch device 3a, and the second driving shaft 6 can be directly rotated by the drivingpower of the engine E without through the power transmitting system ofthe converter 1 and can be connected to a second clutch device 3 b. Inaddition, the first driving shaft 5 can be a hollow cylindrical memberand the second driving shaft 6 can be rotationally arranged coaxiallywithin the first driving shaft 5. Thus, the first driving shaft 5 can berotatable around the second driving shaft 6 and, on the other hand, thesecond driving shaft 6 is rotatable within the first driving shaft 5.The first driving shaft 5 and the second driving shaft 6 can beindependently rotated by properly selected operation of the clutchmechanism 3.

The clutch mechanism 3 can comprise the first clutch device 3 a operableon advancement of an automobile (vehicle) and configured to transmit thedriving power of the engine (driving source) E to the wheels (drivingwheels D) through a power transmitting system of the torque converter 1in a first power transmitting condition, and a second clutch device 3 bconfigured to transmit the driving power of the engine E to the wheels Dwithout through the power transmitting system of the torque converter 1in a second power transmitting condition. The first and second clutchdevices 3 a and 3 b respectively can comprise a plurality of drivingclutch discs 3 aa and 3 ba and a plurality of driven clutch discs 3 aband 3 bb slidable to right and left directions in drawings, and thuseach form multiple disc clutches.

In the first clutch device 3 a, the driving clutch discs 3 aa can bemounted on an interlocking member 15 connected to the first drivingshaft 5 and interlocking therewith and the driven clutch discs 3 ab canbe mounted on a housing 17, and the driving clutch discs 3 aa and thedriven clutch discs 3 ab can be alternately arranged with each other toform a laminated structure. These driving clutch discs 3 aa and thedriven clutch discs 3 ab can be engaged and disengaged with each other.FIG. 5 shows a condition in which the first clutch device 3 a isactuated and the driving clutch discs 3 aa and the driven clutch discs 3ab are press-contacted with each other.

Meanwhile, in the second clutch device 3 b, the driving clutch discs 3ba can be mounted on an interlocking member 16 connected to the seconddriving shaft 6 and interlocking therewith and the driven clutch discs 3bb can be mounted on the housing 17, and the driving clutch discs 3 baand the driven clutch discs 3 bb can be alternately arranged with eachother to form a laminated structure. These driving clutch discs 3 ba andthe driven clutch discs 3 bb can be engaged and disengaged with eachother. FIG. 6 shows a condition in which the second clutch device 3 b isactuated and the driving clutch discs 3 ba and the driven clutch discs 3bb are press-contacted with each other. The term “disengaged” usedherein means a condition in which a pressure applied to the clutch discsis released while the clutch discs may remain in contact with eachother, for example, while slipping. Thus, the term “disengaged” is notlimited only to a physically disengaged condition. The transmission ofdriving power is allowed under the press-contacted condition and cut offunder the disengaged condition.

As shown in FIG. 3, the clutch mechanism 3 can comprise the first clutchdevice 3 a, the second clutch device 3 b, and two hydraulic pistons P1and P2 corresponding respectively to the first and second clutch devices3 a and 3 b contained in the same housing 17. The first and secondclutch devices 3 a and 3 b can thus be selectively actuated bycontrolling the hydraulic pressure for actuating the hydraulic pistonsP1 and P2.

For example, the hydraulic piston P1 can be moved toward the right inFIG. 3 against an urging force of a return spring 3 c by supplying theoperating oil into a hydraulic chamber S1 between the housing 17 and thehydraulic piston P1 and thus the first clutch device 3 a is pressed bytips formed on the hydraulic piston P1 to press-contact the drivingclutch discs 3 aa and the driven clutch discs 3 ab against each other.The tips formed on the hydraulic piston P1 can be passed throughrecesses formed on the peripheries of the driving clutch discs 3 ba andthe driven clutch discs 3 bb of the second clutch device 3 b as shown inFIG. 4.

The hydraulic piston P2 can be moved toward the right in FIG. 3 againstan urging force of a return spring 3 c by supplying the operating oilinto a hydraulic chamber S2 between the hydraulic piston P1 and thehydraulic piston P2 and thus the second clutch device 3 b is pressed bytips formed on the hydraulic piston P2 to press-contact the drivingclutch discs 3 ba and the driven clutch discs 3 bb against each other.Thus the first clutch device 3 a and the second clutch device 3 b can beselectively actuated by controlling the hydraulic pressures operatingthe hydraulic pistons P1 and P2. In other words, the pistons P1 and P2can change the first and second clutch devices between engaged anddisengaged states. In FIG. 3 a reference numeral 21 denotes stoppersarranged at the sides of the first and second clutch devices 3 a, 3 b.Provision of the stopper 21 at the side of the second clutch 3 b enablesthe second and first clutch devices 3 b, 3 a to be operatedindependently from each other.

The housing 17 forming part of the clutch mechanism 3 can be connectedto an interlocking member 18 having formed thereon a gear G1 mating witha gear G2 formed on the output shaft 9. Thus, the driving power of theengine E transmitted through the first and second clutch devices 3 a and3 b can be transmitted to the output shaft 9 through the housing 17 andthe interlocking member 18.

The oil pump 31 can be driven by the driving power of the engine E tosupply oil (operating oil) to the clutch mechanism 3 (first and secondclutch devices 3 a and 3 b) and the torque converter 1 (and also to acontinuously variable transmission (CVT) 25 described below) in order tooperate the clutch mechanism 3 and the torque converter 1. The oil pump31 can discharge oil using the driving power of the engine E and can beconfigured to be always operated during running of the engine E andstopped when the engine E is stopped.

The clutch control device 4 can be configured to selectively operate thehydraulic pistons P1, P2 by introducing operating oil into the hydraulicchambers S1, S2 in accordance with conditions (e.g. speed orinclination) of an automobile (a vehicle) to selectively operate thefirst clutch device 3 a or the second clutch device 3 b in order totransmit the driving power of the engine E to the driving wheels D viathe power transmitting system of the torque converter 1 (first powertransmitting condition) or without the power transmitting system of thetorque converter 1 (second power transmitting condition).

On the other hand, the third clutch device 8 can comprise a multipledisc clutch and can be configured to transmit the driving power of theengine E to the driving wheels D via the power transmitting system ofthe torque converter 1 during reverse-direction operation of a vehicle.That is, the driving power of engine E can be transmitted to the thirdclutch device 8 with a gear G3 formed on an interlocking member 15 matedwith a gear G4 formed on an interlocking member 19 of a side of outputshaft 9 via an idle gear (not shown) arranged between them when a shiftlever (not shown) of a vehicle is shifted to the “R” range (reverseposition).

Similar to the first and second clutch devices 3 a, 3 b, the thirdclutch device 8 can have a housing 20 connected to the output shaft 9and interlocked therewith. A hydraulic piston P3 and alternatelyarranged driving clutch discs 8 a and driven clutch discs 8 b can bearranged within the housing 20 so that mutually adjacent driving clutchdiscs 8 a and driven clutch discs 8 b are engaged and disengaged witheach other by actuation of the hydraulic piston P3.

The engine control device 22 can be formed, for example, within an ECU(not shown) for controlling the engine E and can be configured toautomatically stop the engine E to have an “idle-stop” condition whenthe speed of a vehicle is reduced below a predetermined value (e.g. avehicle has reached a speed between a speed just before stop and a fullstop) and to restart the engine E when a brake operation is released oran accelerator pedal is depressed. The engine control device 22 can bededicated to control of the engine E relating to the idle-stop operationwhile the ECU generally controls operations of the engine E. In someembodiments, the engine E can be restarted after the idle-stop in otheradditional or different conditions, such as an increase of the vehiclespeed etc. for example.

Where the power transmitting apparatus comprises the clutch controldevice 4 for transmitting the driving power of the engine E to thedriving wheels D through the power transmitting system of the torqueconverter 1 or for transmitting the driving power of the engine E to thedriving wheels D without the power transmitting system of the torqueconverter with proper selected operation of the first clutch device 3 aor the second clutch device 3 b in accordance with conditions of thevehicle, it is possible to avoid complication and increases in size ofthe apparatus, to improve the starting performance using the torqueamplifying function of a torque converter, and to improve the powertransmitting efficiency during steady running of a vehicle. Accordingly,in some embodiments it is possible to eliminate a lock-up clutch of theprior art.

Furthermore, since the first driving shaft 5 and the second drivingshaft 6 are arranged coaxially with each other, it is possible to reducea whole size of the power transmitting apparatus as compared with aconfiguration in which they are separately and linearly extended as inthe prior art. In addition, since the second driving shaft 6 isconnected to the engine E through a damper mechanism 7 for dampingtorque variation, it is possible to damp vibration of the engine Etransmitted to the second clutch device 3 b.

In addition, since the clutch mechanism 3 is configured so that thefirst and second clutch devices 3 a, 3 b and two hydraulic pistons P1,P2 corresponding to the first and second clutch devices 3 a, 3 b arecontained within the same housing 17 and that the first and secondclutch devices 3 a, 3 b can be selectively operated by controlling thehydraulic pistons P1, P2, it is possible to further reduce the size andsimplify the structure of whole the power transmitting apparatus.

The variable speed unit A can be a continuously variable transmission(CVT) 25. More particularly, as shown in FIG. 8, the CVT 25 can beoperatively positioned between the second clutch device 3 b of theclutch mechanism 3 and the driving wheels D in the power transmittingsystem to transmit power from the engine E to the driving wheels D.

Such a CVT 25 can comprise two pulleys Q1, Q2 and a belt V extendingtherebetween and can achieve a desired speed by independently shiftingmovable sheaves and changing diameters of the pulleys Q1, Q2 on whichthe belt V runs by a hydraulic pressure control circuit 24. The CVT 25can be supplied with operating oil from the oil pump 31 to shift themovable sheaves of the pulleys Q1, Q2. The clutch control device 4 canbe electrically connected with a brake switch S1, a position sensor S2and engine control device 22 etc. The CVT 25 can be controlled by theclutch control device 4 via the hydraulic pressure control circuit 24. Areference character S3 denotes a throttle opening sensor of theaccelerator pedal.

Since the CVT 25 is operatively positioned between the second clutchdevice 3 b of the clutch mechanism 3 and the driving wheels D in thepower transmitting system to transmit power from the engine E of thevehicle to the driving wheels D, a clutch used for advancing a vehicleand a clutch for transmitting the driving power of the engine E to thedriving wheels D without the power transmitting system of the torqueconverter 1 can be combined in the second clutch device 3 b. A referencecharacter F denotes a differential gear of a vehicle. A referencecharacter S4 denotes an engine speed sensor configured to detect therotational speed of the engine E. A reference character S5 denotes aspeed sensor configured to detect the rotational speed of the firstdriving shaft 5. A reference character S6 denotes a oil pressure switchconfigured to detect the hydraulic pressure of the clutch mechanism 3(the second clutch device 3 b in this embodiment). A reference characterS7 denotes a secondary shaft speed sensor. A reference character S8denotes a counter shaft speed sensor.

As shown in FIG. 9, the hydraulic pressure control circuit 24 cancomprise oil paths and valves connecting the oil pump 31 and objects tobe supplied with oil (e.g. the torque converter 1, the clutch mechanism3, etc.) and solenoids for opening and closing the valves. A referencenumeral 26 denotes a regulator valve for controlling the line pressure.A reference numeral 27 denotes a linear solenoid (LS B) for controllingthe pressure of the regulator 26. A reference numeral 28 denotes alinear solenoid (LS A) for controlling the clutch pressure. A referencenumeral 32 denotes a manual valve for switching the oil paths inaccordance with the shift ranges (P, R, N, D) of the variable speedunit. The linear solenoid (LS A) 28 can control the clutch pressure forthe clutch mechanism 3 in the D range and the clutch pressure for a “RVSCLUTCH” in the R range. The linear solenoid (LS B) 27 can control theline pressure controlled by the regular valve.

As shown in this embodiment, a flow control device 23 can be positionedin an oil path from the oil pump 31 to the torque converter 1. The flowcontrol device 23 can be configured to limit the supply of oil to thetorque converter 1 by the oil pump 31 and to prioritize the supply ofoil to the clutch mechanism 3 and the continuously variable transmission(CVT) 25 when the vehicle speed is reduced below a predetermined valueunder a fuel-cut-off condition (fuel supply is stopped) of the engineduring vehicle speed reduction.

More particularly, the flow control device 23 can comprise a hydraulicvalve mechanism having a first supply path 23 a for normally supplyingoil to the torque converter 1, a second supply path 23 b in which anorifice 23 ba for limiting the supply of oil is formed, and a valve 23 cfor opening and closing the first supply path 23 a by hydraulicpressure. The valve 23 c can be opened and closed by a solenoid (SH A)29 and a solenoid (SH B) 30. The valve 23 c of the flow control device23 of this embodiment can be normally urged by a spring in a directionthat would close the first supply path 23 a. Although in this embodimentthe oil supply to the torque converter 1 by the oil pump 31 is limitedby the flow control device 23 when vehicle speed is reduced below apredetermined value with fuel to the engine E being cut off duringvehicle speed reduction, the supply of oil to the clutch mechanism 3(the second clutch device 3 b in this embodiment) and the CVT 25 can beprioritized by preventing supply of any oil to the torque converter 1.

As shown in FIG. 10, the clutch control device 4 can be configured sothat the hydraulic pressure valve mechanism forming the flow controldevice 23 can be selectively operated by controlling the solenoid (SH A)29 and the solenoid (SH B) 30 in accordance with set modes. In FIG. 10marks “o” denote that the solenoid is electrically “ON” and marks “x”denote that solenoid is electrically “OFF.” In addition, a term “LinePressure” denotes that the line pressure is directly inputted to theclutch mechanism 3 and a term “Linear solenoid A” denotes that thelinear solenoid valve (LS A) 28 controls the clutch pressure.

FIG. 11 is a time chart illustrating control by the clutch controldevice 4 in speed reduction, stop, and acceleration processes. This timechart indicates that the supply of oil to the clutch mechanism 3 and theCVT 25 is prioritized by limiting supply of oil by the oil pump 31 tothe torque converter 1 when vehicle speed is reduced below apredetermined value (a second vehicle speed Vb in FIG. 11) with fuel tothe engine E being cut off during vehicle speed reduction.

In some embodiments, such as in this embodiment, the clutch controldevice 4 can be configured to actuate only the second clutch device 3 bwhen a vehicle speed is reduced below a predetermined value (a secondvehicle speed Vb in FIG. 11) with fuel to the engine E being cut offduring vehicle speed reduction. In addition, when the vehicle speed isfurther reduced to a predetermined value (a first vehicle speed Va inFIG. 11), operation of the second clutch device 3 b is stopped at thesame time as the engine is idle-stopped. Since the clutch control device4 actuates only the second clutch device 3 b when a vehicle speed isreduced below a predetermined value (a second vehicle speed Vb in FIG.11) with fuel to the engine E being cut off during vehicle speedreduction, oil can be supplied more reliably and smoothly than aconfiguration in which both the first and second clutch devices 3 a, 3 bare supplied with oil.

Furthermore, the engine control device 22 performs an idle-stop when thetransmission ratio of the CVT 25 is a predetermined value (transmissionratio necessary for beginning of vehicle movement) or more. Thus,driving power for initiating vehicle movement at the restart of theengine after the idle-stop can be reliably provided.

Instead of using the flow control device 23, a line pressure regulatedby the regulator valve 26 can be increased as shown in FIG. 12 bycontrolling the linear solenoid valve (LS B) 27 between the secondvehicle speed Vb and the first vehicle speed Va. Also, in this case itis preferable to control the regulator valve 26 so that the linepressure is returned to an ordinary value when a vehicle reach the firstvehicle speed Va and become the idle-stop condition (see line pressuresetting illustrated in FIG. 12).

A control method of the engine control device 22 is described withreference to a flowchart shown in FIG. 13. At S1, it is determinedwhether or not the ignition is “ON.” If “ON”, the method proceeds to S2and determines whether or not it is in idle-stop. If determined to be inidle-stop, it is determined in S3 whether or not the accelerator pedalis depressed. If determined to be depressed, the method proceeds to S4and the engine is restarted.

On the other hand, if determined in S3 that the accelerator pedal is notdepressed yet, the method goes to S5 and determines whether the vehiclespeed has been increased. If the vehicle speed has been increased, themethod goes to S4 and the engine is restarted. On the contrary, if thevehicle speed has not been increased, the method goes to S6 anddetermines whether a predetermined duration of the idle-stop has lapsed.If the predetermined duration of the idle-stop has lapsed in S6, themethod goes to S4 and the engine is restarted. On the contrary, if thepredetermined duration of the idle-stop has not lapsed, the method goesto S7 and determines whether the vehicle speed is “0” (i.e. stopped) ornot. If determined in S7 that the vehicle speed is “0”, the method goesto S8 and determines whether the brake is “OFF” or not. If the brake is“OFF”, the method goes to S4 and the engine is restarted.

If it is determined in S2 that it is not in idle-stop, the method goesto S9 and determines whether it is in the restart of the engine or not.If it is determined that it is in the restart of the engine, the methodgoes to S10 and determines whether the restart of the engine has beencompleted. If it is determined that the restart of the engine has beencompleted, the method goes to S11 and engine operation (engine runningor engine driving) is performed. On the contrary, if it is determinedthat the restart of the engine has not been completed, the method goesto S4 and the engine is restarted.

If it is determined in S9 that it is not in the restart of the engine(i.e. in engine running), the method goes to S12 and determines whetheror not the transmission ratio (effective gear ratio) of the continuouslyvariable transmission (CVT) 25 is a predetermined value or greatervalue. If determined that the transmission ratio of the CVT 25 is apredetermined value or greater value, the method goes to S13 anddetermines whether that the idle-stop conditions (e.g. the vehicle speedis a predetermined value or less, the temperatures of water and oil arepredetermined values or more, no trouble, etc.) are satisfied or not. Ifthe transmission ratio of the CVT 25 is not a predetermined value orgreater value, the method goes to S11 and the engine operation (enginerunning or engine driving) is performed. If it is determined in S13 thatthe idle-stop conditions are satisfied, the method goes to S14 and theidle-stop condition is implemented.

A control method of the clutch control device 4 is described withreference to a flowchart shown in FIG. 14.

First, it is determined in S1 whether the engine is in the idle-stop ornot. If it is in the idle-stop, the second clutch device 3 b is made“OFF” (S2), the first clutch device 3 a is made “OFF” (S3), and thesupply of oil to the torque converter 1 is also made “OFF” (S4). On thecontrary, if it is determined in S1 that the engine is not in theidle-stop, the method goes to S5 and determined whether it is in therestart of the engine or not. If it is in the restart of the engine, themethod goes to S6 and determined whether a predetermined time has lapsedfrom the restart of the engine.

If it is determined in S6 that the predetermined time has not lapsedfrom the restart of the engine, the method goes to S7 and determineswhether or not the engine speed is a predetermined value or greatervalue. If the engine speed is not the predetermined value or greatervalue, the method goes to S8 and determines whether the oil pressureswitch S6 (detecting device) is “ON” or not. If the oil pressure switchS6 is not “ON”, the method goes to S9 and determines whether or not theclutch slip ratio is a predetermined value or greater value. If theclutch slip ratio is not the predetermined value or greater value, themethod goes to S10 and actuates the second clutch device 3 b. After thesecond clutch device 3 b is actuated in S10, the method goes to S3 andS4.

On the contrary, if it is determined in S6 that the predetermined timehas lapsed from the restart of the engine, or if it is determined in S7that the engine speed is the predetermined value or greater value, or ifit is determined in S8 that the oil pressure switch S6 (detectingdevice) is “ON”, or if it is determined in S9 that the clutch slip ratiois a predetermined value or greater value, the method goes to S11 andactuates the second clutch device 3 b. Then after it actuates the firstclutch device 3 a in S12, supply of hydraulic oil to the torqueconverter 1 is made “ON” in S13.

If it is determined in S5 that it is not in the restart of the engine(i.e. in engine running), the method goes to S14 and determines whetherthe accelerator pedal is “OFF” or not. If the accelerator pedal is“OFF”, the method goes to S15 and determines whether it is in speedreduction or not. If it is determined in step S15 that it is in thespeed reduction, the method goes to S16 and determines whether thevehicle speed is slower than a predetermined value (second speed Vb) ornot. If the vehicle speed is lower than the second speed Vb, the secondclutch device 3 b is made “ON” in 517, the first clutch device 3 a ismade “OFF” in S18, and the supply of operating oil to the torqueconverter 1 is made “OFF” in S19. In addition, if it is determined inS14 that the accelerator pedal is not “OFF” (i.e. is “ON”), in S15 thatit is not in the speed reduction, and in S16 that the vehicle speed isnot lower (i.e. is higher) than the predetermined value (second speedVb), it goes to S11 and then S12 and S13 after the second clutch device3 b has been actuated.

In some embodiments, such as this embodiment, where the powertransmitting apparatus comprises a flow control device configured tolimit or prevent the supply of oil to the torque converter 1 by the oilpump 31 and to prioritize the supply of oil to the clutch mechanism 3(second clutch device 3 b) and the continuously variable transmission(CVT) 25 when the vehicle speed is reduced below a predetermined value(second vehicle speed Vb) with fuel being cut off by the engine controldevice during vehicle speed reduction, it is possible in a powertransmitting apparatus for a vehicle mounted with a torque converter 1and an idle-stop mechanism to improve fuel economy without cancellingthe fuel-cut-off during vehicle speed reduction and to reduce themanufacturing cost by eliminating an electrically driven oil pump.

In addition, where the flow control device 23 comprises a hydraulicvalve mechanism having a first supplying path 23 a configured tonormally supplying oil to the torque converter, a second supplying path23 b configured to limit or prevent the supply of oil, and a valve 23 cconfigured to open and close the first supply path 23 a by hydraulicpressure, it is possible instantly and smoothly switch between thecondition in which the supply of oil to the torque converter 1 islimited or prevented and the condition in which the supply of oil to thetorque converter 1 is not limited or prevented. Furthermore, where thevalve 23 c is normally urged by a spring in a direction for closing thefirst supplying path 23 a, the supply of oil to the torque converter canbe reliably limited or prevented regardless of the set operationpressure of the valve 23 c even though the control pressure has beenreduced because of reduced pump rotation when the vehicle speed isreduced below a predetermined value (second vehicle speed Vb) in afuel-cut-off condition.

A second embodiment of a power transmitting apparatus, like the firstembodiment, can be configured to transmit or cut-off the driving forcefrom an engine (driving source) of an automobile (vehicle) to or fromthe wheels (driving wheels). Such an apparatus can include, withreference to FIGS. 1 and 2, a torque converter 1, a clutch mechanism 3,an oil pump 31, a clutch control device 4, a engine control device 22, aflow control device 23, a first driving shaft 5, a second driving shaft6, a damper mechanism 7, and a third clutch device 8, and a variablespeed unit A (continuously variable transmission (CVT) 25). The samereference numerals are used to designate structural elements in thisembodiment as those used to designate similar structural elements in thefirst embodiment and therefore detailed description of them is notrepeated.

In this second embodiment, an accumulator 33 can be operativelypositioned on an oil supply path of the clutch mechanism 3 from the oilpump 31 as shown in FIG. 15. The accumulator 33 can be configured toaccumulate the oil and can be configured so that the oil accumulated inthe accumulator 33 is discharged therefrom to the clutch mechanism 3(second clutch device 3 b in this embodiment) and the continuouslyvariable transmission (CVT) 25 when the vehicle speed is reduced below apredetermined value (second vehicle speed Vb) with fuel to the engine Ebeing cut off during vehicle speed reduction. The provision of theaccumulator 33 enables the oil supply to the clutch mechanism 3 and theCVT 25 to be more reliable and smooth. A reference numeral 34 in FIG. 15denotes a check valve.

The timing of discharging the oil accumulated in the accumulator 33 isnot limited only to that at which the vehicle speed is reduced to apredetermined value (second vehicle speed Vb) but also can be at timeswhen the vehicle speed is reduced to the first vehicle speed Va or less(after beginning the idle-stop) as shown in a time chart of FIG. 16. Inthis case it is preferable to control the CVT 25 so that itstransmission ratio is kept constant. This reduces the need for pressureaccumulation and, thus, allows the capacity of the accumulator 33 to bereduced. In addition, in this embodiment, the supply of oil to theclutch mechanism 3 can be prioritized by actuating the flow controldevice 23 through ON/OFF control of the solenoid (SH A) 29 and thesolenoid (SH B) 30 and limiting the oil supply rate by the oil pump 31to the torque converter 1 on restart of the engine E after theidle-stop.

Other configurations of the accumulator 33 can be used if it isconnected operatively on the oil supply path of the clutch mechanism 3from the oil pump 31 and the accumulated oil can be supplied to theclutch mechanism 3 and the CVT 25 by discharging it from the accumulator33 when the vehicle speed is reduced to the predetermined value (secondvehicle speed Vb) or less with fuel to the engine E being cut off duringvehicle speed reduction.

A third embodiment of a power transmitting apparatus, like the first andsecond embodiments, can be configured to transmit or cut-off the drivingforce from an engine (driving source) of an automobile (vehicle) to orfrom the wheels (driving wheels). Such an apparatus can include, withreference to FIG. 17, a torque converter 1, a clutch mechanism 3′, anoil pump 31, a clutch control device 4, a engine control device 22, aflow control device 23, a damper mechanism 7, and a reverse clutchdevice 3′c, and a variable speed unit A (continuously variabletransmission (CVT) 25). The same reference numerals are used todesignate structural elements in this embodiment as those used todesignate similar structural elements in the first and secondembodiments and therefore detailed description of them is not repeated.

The clutch mechanism 3′ can comprise a forward-operation clutch device3′a operated during forward vehicle operation and configured to transmitthe driving power of the engine E to the driving wheels D via the powertransmitting system of the torque converter 1 (the first powertransmitting condition) and a lock-up clutch device 3′b configured totransmit the driving power of the engine E to the driving wheels Dwithout the power transmitting system of the torque converter 1 (thesecond power transmitting condition), and the clutch control device 4 isconfigured to selectively operate the forward-operation clutch device3′a and the lock-up clutch device 3′b in accordance with a condition ofa vehicle to position them in either the first power transmittingcondition or the second power transmitting condition.

The lock-up clutch device 3′b can be arranged within the torqueconverter 1 and can be configured to be connected to the turbine T ofthe torque converter 1 so that the torque converter cover and theturbine are directly connected via a clutch piston. The powertransmitting apparatus of this third embodiment can be easily applied toa vehicle mounted with a lock-up clutch device (lock-up clutch) beingcomparatively in wide use.

The power transmitting apparatus of the present inventions have beendescribed with reference to exemplifying embodiments. However, thepresent inventions are not limited to these illustrated embodiments andthe clutch devices can be formed in other configurations.

1. A power transmitting apparatus, comprising: a torque converter havinga torque amplifying function; a clutch mechanism configured to bepositioned in a first power transmitting condition in which drivingpower of an engine is transmitted to driving wheels of a vehicle via apower transmitting system of the torque converter and a second powertransmitting condition in which the driving power of the engine istransmitted to the wheels without the power transmitting system of thetorque converter; an oil pump driven by the driving power of the engineto supply oil to the clutch mechanism and the torque converter tooperate them; a continuously variable transmission supplied with oil bythe oil pump to actuate pulleys by hydraulic pressure of the oil tocontinuously vary a transmission ratio of the continuously variabletransmission; a clutch control device configured to selectively operatethe clutch mechanism in accordance with a vehicle condition to positionthe clutch mechanism in either the first power transmitting condition orthe second power transmitting condition; and an engine control deviceconfigured to idle-stop the engine by automatically stopping the enginewhen vehicle speed is reduced below a predetermined value and to restartthe engine when an accelerator pedal is depressed or brakes are releasedduring an idle-stop condition of the engine.
 2. The power transmittingapparatus of claim 1, wherein the engine control device is configured toautomatically stop the engine when the vehicle speed is reduced to apredetermined value while the vehicle is slowing down.
 3. The powertransmitting apparatus of claim 1, wherein the engine control device isconfigured to idle-stop the engine when the transmission ratio of thecontinuously variable transmission is a predetermined value or more. 4.The power transmitting apparatus of claim 1, wherein the engine controldevice is configured to idle-stop the engine when both a watertemperature and an oil temperature are predetermined values or more. 5.The power transmitting apparatus of claim 1, wherein the engine controlis configured to restart the engine when a predetermined duration oftime of the idle-stop condition has lapsed.
 6. The power transmittingapparatus of claim 1, wherein the engine control device is configured tostart the engine when a vehicle speed of the vehicle has been increasedduring the idle-stop condition.
 7. The power transmitting apparatus ofclaim 1, wherein the engine control device is configured to not startthe engine, irrespective of release of braking operation, when thevehicle speed is not zero in the idle-stop condition.
 8. The powertransmitting apparatus of claim 1, further comprising a hydraulic valvemechanism having a first supplying path for supplying oil to the torqueconverter during an ordinary operation, a second supplying pathconfigured to limit or inhibit the supply of oil to the torqueconverter, and a valve for opening and closing the first supplying pathby hydraulic pressure; and a plurality of solenoids configured toselectively operate the hydraulic valve mechanism, the solenoids beingset to an “OFF” state during the idle-stop condition.
 9. The powertransmitting apparatus of claim 1, further comprising an accumulatorconfigured to accumulate oil, the accumulator being configured so thatthe oil accumulated in the accumulator is discharged therefrom to theclutch mechanism and the continuously variable transmission when thevehicle speed is reduced below a predetermined value with the enginebeing fuel-cut during a process of speed reduction of the vehicle.